Introductory Chemistry Practice, Set Where Biology Uses It
by Professor Stephen T. Abedon Steve Abedon, Ph.D., has taught well over 100 individual classes and ~10 individual courses (including introductory biology, microbiology, physiology, biochemistry, etc.) over his 30+ years as a college professor. He has over 150 publications, including multiple monographs, and is ranked in the top 1 or 2 percent among researchers of all disciplines worldwide. His research focuses on bacteriophage biology and phage therapy. (abedon.1@osu.edu)
phage.org | phage-therapy.org | biologyaspoetry.org | abedon.phage.org | google scholar | publications
Jump to: 🗺️ Topic Map | 📏 Measurement | ⚛️ Atoms | 🧪 Formulas and Names | 🔗 Bonding and Shapes | ⚖️ Moles | ⚗️ Reactions and Redox | 🔢 Stoichiometry | 🔥 Energy | 🎈 Gases | 💧 Solutions | ⇄️ Rates and Equilibrium | 🍋 Acids and Bases | ☢️ Nuclear Chemistry | ⬡ Organic Chemistry | 🏷️ IUPAC Names | 🧬 Biological Chemistry | 📝 Word Problems | 🧮 More Calculators
biologyaspoetry.org/laboratories/chemistry/ · Abedon’s Books
How can I improve this page? contact: chemistry@biologyaspoetry.org
Type a word or two, such as , and choose a match to go straight to it. The search covers every skill’s name, the other words students use for it, and its how-to text, as well as the page’s sections.
Every skill on this page is listed below by tab, with a mark where a biology version of its problems is available. Pick a skill and press Practice, or go straight to a tab.
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The page follows the usual one-semester introductory chemistry course for students who are not chemistry majors, often called general, organic, and biological chemistry. It does not try to cover a course for chemistry majors. Organic and biological chemistry are covered at the level of recognizing functional groups, naming the simpler organic compounds by the IUPAC rules, predicting the products of a few reaction types, and the basic chemistry of biomolecules; drawing full structures, isomers, and the pathways of metabolism are left to your textbook. The order of topics differs from school to school and from instructor to instructor, so your own syllabus is the final word.
Something missing? If your course covers a topic that isn’t here, if a problem doesn’t match the way your course does it, or if an answer you believe is right is marked wrong, say so at chemistry@biologyaspoetry.org. The page grows from what students ask for.
The page remembers the tab you were on and, on each tab, the skill, the problem, any answer you had typed, and how you have been doing. It keeps this in your web browser on this device only; nothing is sent anywhere. Using another browser or device starts fresh.
The answer box reads chemistry the way you would type it in most online homework systems. A few conventions help:
Answers are judged by significant figures. An answer with the right value but too many or too few significant figures is marked as such rather than simply wrong, and a last digit that is off by one, the usual result of rounding along the way, is accepted. pH values are judged by decimal places instead, for the reason given on the Acids and Bases tab. Atomic masses here are rounded the way most textbook tables round them (C = 12.01, O = 16.00, H = 1.008), and each problem lists the values it uses; a table that rounds differently can change the last digit of an answer.
Your answers to the practice problems are kept as you go, grouped by skill. In most browsers they are still here if you leave and come back on the same device, though a private window, a different device, or cleared browser data will start you fresh. When you are done, download a summary to hand in or keep. It lists each problem you checked, the answers you gave, and whether the first one was right, and it notes when a hint or steps of the worked solution were showing before you answered. A guided problem counts as right the first time only if every step was. These answers are kept apart from your saved place: starting over above does not clear them, and clearing them does not change your place or the running count on each practice card.
Every number in chemistry is a measurement or comes from one, and a measurement is only as good as its precision. This tab covers significant figures, metric conversions, converting units by dimensional analysis, density, and temperature scales.
Biology measures in micrometers, microliters, and milligrams, and clinical work adds pounds, drops per minute, and doses per kilogram of body weight. Moving correctly between them comes down to setting up conversion factors so that units cancel. For scientific notation itself, see the Numbers tab of the companion page, Basic Math for Biology.
A tip that helps on every tab: estimate before you calculate. If 250 mL is a quarter of a liter, an answer of 4 L for its volume announces a slip at once.
An element is defined by the number of protons in its atoms. Isotopes of an element differ only in their neutrons, and ions differ from atoms only in their electrons. This tab covers counting those particles, finding an element’s average atomic mass from its isotopes, writing electron configurations, and predicting valence electrons and ion charges from the periodic table.
Biology runs on ions: sodium, potassium, calcium, and chloride ions carry nerve impulses and trigger muscle contraction. Isotopes, heavy or radioactive, are used to trace atoms through living things.
Chemical formulas and names are the vocabulary of chemistry. An ionic compound combines positive and negative ions in the ratio that cancels their charges; a molecular compound of two nonmetals is named with prefixes that count its atoms.
Bone mineral, the salts of blood, many supplements, and laboratory buffers are ionic compounds, and their polyatomic ions (phosphate, hydrogen carbonate, sulfate, nitrate) turn up throughout biochemistry. Carbon dioxide and nitric oxide are molecular.
The naming rules on this tab, like those on the IUPAC Names tab, are set by IUPAC, the International Union of Pure and Applied Chemistry.
Atoms share electrons in covalent bonds and transfer them in ionic bonds, and the difference in their electronegativities says which. A Lewis structure shows where a molecule’s electrons are; from it, VSEPR theory predicts the molecule’s shape, and the shape decides whether the molecule is polar and which forces hold its molecules together.
Water is bent and polar, so it dissolves salts and sugars and hydrogen-bonds to itself; the hydrocarbon tails of fats are nonpolar, so they don’t. Much of biology, from membranes to protein folding to DNA’s double helix, follows from these differences.
A mole is a counting unit, 6.022 × 1023 of anything, and the molar mass of a substance is the mass of one mole of it. Moles connect the grams a balance can weigh to the numbers of atoms and molecules that actually react.
Doses, nutrients, and reagents are weighed in grams or milligrams, but what they do depends on how many molecules are present.
A chemical equation is balanced when every element has the same number of atoms on both sides. Balancing changes only the coefficients in front of formulas, never the subscripts within them, since changing a subscript changes the substance. This tab also covers oxidation–reduction (redox) reactions, in which electrons pass from one substance to another, tracked with oxidation numbers.
The overall equations of metabolism (respiration, photosynthesis, fermentation) are balanced equations, and their coefficients are the basis for every calculation of how much is used and how much is made.
Stoichiometry uses a balanced equation to calculate how much of one substance reacts with, or is made from, another. The coefficients give mole ratios, and molar masses convert between moles and grams.
How much carbon dioxide comes from burning a gram of sugar, how much ethanol yeast can make, and which nutrient runs out first in a culture are stoichiometry questions. Guided, step-by-step versions are on the Word Problems tab.
Energy is measured in joules or calories, and the heat needed to change the temperature of a substance depends on its mass and its specific heat. A chemical reaction releases or absorbs heat in proportion to how much reacts, given by its heat of reaction, ΔH.
A food Calorie is a kilocalorie, and the high specific heat of water is part of why bodies, lakes, and oceans hold their temperatures steady.
The gas laws relate the pressure, volume, temperature, and amount of a gas. In every gas law, temperatures must be in kelvins.
Breathing, diving, altitude, and the oxygen and carbon dioxide exchanged by cells and leaves are all gas-law problems.
A concentration says how much solute a solution holds in a given volume: molarity in moles per liter, percent (m/v) in grams per 100 mL. Diluting trades concentration for volume while keeping the amount of solute the same.
Making buffers, growth media, and drug solutions is daily work in a biology laboratory, and intravenous fluids must match the osmolarity of blood.
Many reactions run in both directions and settle at an equilibrium, where the forward and reverse rates are equal. The equilibrium constant, K, describes where that balance lies, the reaction quotient, Q, says which way a mixture will go to reach it, and Le Châtelier’s principle predicts how an equilibrium responds when it is disturbed.
Hemoglobin loading and unloading oxygen, the bicarbonate buffer of blood, and the reversible steps of metabolism are all equilibria. How fast a reaction gets there is a separate question, of rates: temperature, concentration, and catalysts such as enzymes. The Acids and Bases tab builds on this one.
pH is the negative logarithm of the hydronium ion concentration, so each pH unit is a tenfold change. In water the concentrations of H3O+ and OH− are tied together, and a titration measures an acid’s concentration by neutralizing it. An acid that gives up H+ becomes its conjugate base; strong acids do so completely and weak acids only partly; and a weak acid mixed with its conjugate base makes a buffer.
Blood, the stomach, lysosomes, and soils each hold their own pH, and most enzymes work only within a narrow range. For logarithms themselves, see the Exponentials and Logs tab of Basic Math for Biology.
Radioactive nuclei decay by giving off particles and energy. In a nuclear equation, mass numbers balance and so do atomic numbers, and each radioactive isotope decays with its own half-life.
Medicine images with technetium-99m and fluorine-18 and treats with iodine-131 and radium-223, and archaeology dates with carbon-14.
Organic chemistry is the chemistry of carbon compounds. Carbon forms four bonds and links to itself in chains and rings, and the groups of other atoms attached to those chains, the functional groups, decide how a molecule behaves. This tab covers recognizing functional groups, writing molecular formulas, and predicting the products of the common reaction types.
Nearly every molecule in a cell is organic, and the reactions of metabolism are the same reaction types run by enzymes: oxidation and reduction, hydration, and the formation and hydrolysis of esters and amides.
Naming organic compounds by the IUPAC rules has a tab of its own, IUPAC Names.
IUPAC, the International Union of Pure and Applied Chemistry, sets the rules for naming chemical compounds, so that every structure has one systematic name and every name describes one structure. For organic compounds the rules come down to a few questions asked in order: what family is it (which sets the ending), how long is the longest chain that holds the family’s group, or how large is the ring (which sets the root), where numbering starts and which way it runs, and what is attached where.
This tab practices those questions in both directions, from structure to name and from name to structure, and ends with finding the mistakes in names that break a rule. Current IUPAC style places a number just before the ending (pent-2-ene, butan-2-ol); many textbooks still put it in front (2-pentene, 2-butanol). Either style is accepted. Naming ionic and molecular inorganic compounds is on the Formulas and Names tab.
Biological chemistry applies all of this to the molecules of life: carbohydrates, lipids, proteins, and nucleic acids. This tab covers the classes of biomolecules, how polymers are built and broken (one water per bond), base pairing in DNA and RNA, base composition, and saturated and unsaturated fatty acids.
Every problem on this tab is already set in biology, so there is no separate biology version.
Word problems are where chemistry calculations get used, and where they most often go wrong. The problems on this tab are guided. Each step asks you a question before it shows you anything, every conversion is written out with its units, and a wrong choice gets an explanation of why it is wrong, not just a red mark.
If the harder part is working out what a problem is asking in the first place, the companion page Overcoming Biology Anxiety is about exactly that step.